Many kinds of removable band-type couplings for pipes exist in the art. It is noted that throughout the specification and claims, the term “pipe” encompasses any kind of generally cylindrical object.
There is no best coupling for all purposes, so users must choose the features required for a particular application, and then choose the lowest cost coupling meeting those specifications. The variables are many: diameter, diameter variability, degree of sealing required, fluid being transferred, hydraulic pressure, exposure to the outside or not, removable or permanent, weight limitations, space limitations, ease of installation and further factors all of which influence the selection of a coupling.
U.S. Pat. No. 6,293,556 to Krausz describes a coupling for connecting pipes of the same or different diameters. The coupling has a ring shaped seal made of rubber or other resilient material, constructed of a first ring seal seated over a second ring seal. The seals can be easily disconnecting from one another to allow sealing against different diameter pipes. For smaller diameter pipes, both the first and second ring seals are used; for larger diameters, only one seal is used.
U.S. Pat. No. 7,571,940 to Krausz describes another type of pipe coupling that combines an elastomeric seal member (similar, but not identical, to the seal of U.S. Pat. No. 6,293,556) with a grip ring. The grip ring is formed of wedge-shaped grip elements that are radially spaced from one another. The grip elements are formed with teeth that face inwards towards the center of the ring. A single fastener (e.g., bolt and nut or other tightenable screw) is provided, which when tightened in a direction transverse to the axial length of the pipe, presses both the elastomeric seal member and the grip ring against the surface of the pipe.